There used to be quite a lot of third party documentation on m0n0wall captive portal, but it seems to gave aged off the internet. If you find any, let us know!
Jonathan De Graeve implemented a number of RADIUS features for Captive Portal to give it WISPr functionality. Aside from that, these listed features are supported.
Features currently implemented include:
RADIUS-defined URL redirection taking precedence over URL redirection parameter in captive portal setup page.
Multiple RADIUS server support
Failure message on captive portal login error page, plus logging to the captive portal log on why authentication failed (user account exceeded bandwidth limit, bad password, etc.).
Cisco-compatible feature (sending calling-station-id with clientip and called-station-id with clientmac instead of standard behavior calling-station-id and clientmac).
Timeout parameter and max authentication retries parameter
retrieval of user bandwidth settings
retrieval of user group
retrieval of session-timeout
Retrieval means the variable is present and CAN be used, but there is no action bound to it yet.